Circuit breaker with externally adjustable tripping mechanism



Sept. 27, 1966 R. E. LOCHER 3,275,959

CIRCUIT BREAKER WITH EXTERNALLY ADJUSTABLE TRIPPING MECHANISM Filed Dec. 15, 1964 INVENTOR.

R055 E. LOCHER HABQ/S, K/EcH, RUSSELL & A se/v itecl States Patent of California Filed Dec. 15, 1964, Ser. No. 418,406 Claims. (Cl. 335-35) This invention relates to circuit breakers and, in particular, to circuit breakers including new and novel means for adjustment of the trip mechanisms after final assembly.

Electrical circuit breakers utilize a number of small interconnected parts including several springs all mounted within an insulating housing. The housing usually consists of two components such as a case and cover which are permanently joined together at assembly. Circuit breakers may have a thermal trip mechanism, a magnetic trip mechanism, or a combination of thermal and magnetic tripping. The tripping mechanisms ordinarily are adjusted to produce breaker operation at the desired current condition and it is an object of the present invention to provide a new and improved breaker construction in which the tripping mechanism adjustments can be performed after the breaker has been permanently assembled. A further object is to provide such a structure which does not require exposure of the interior of the breaker. An additional object is to provide such a structure in which the adjustment of magnetic tripping or thermal tripping or both can be accomplished quickly and easily using simple tools.

It is an object of the invention to provide a new and improved circuit breaker including a housing with first and second body members joined along an edge, a trip member mounted within the housing for releasing the switch, a mounting bracket carried in the housing, a thermal responsive member mounted on the bracket with a portion disposed for engaging the trip member, and means for inserting between the body members along an edge and engageable with the bracket for varying the position of the bracket and the thermal responsive member relative to the trip member for adjusting the current setting at which the breaker will trip. A particular object is to provide such a structure in which the adjusting lever is a knife-like element insertable at the edge for springing the body members apart permitting entry of the adjusting member to engage the bracket.

It is an object of the invention to provide a circuit breaker including a magnetic structure carried within the housing and a movable armature mounted on the structure and disposed for engaging the trip member, with the magnetic structure incorporating a core threadedly mounted for movement toward and away from the armature and with the housing including an access opening for external positioning of the core by a screwdriver or the like.

It is a particular object of the invention to provide such a circuit breaker incorporating the trip member with the thermal responsive member for actuating the trip member and the magnetic armature for actuating the trip member and means for adjusting each of said trip member actuators from the exterior of the breaker after final assembly.

The invention also comprises novel details of construction and novel combinations and arrangements of parts, which will more fully appear in the course of the following description. The drawing merely shows and the de scription merely describes a preferred embodiment of the present invention which is given by way of illustration or example.

3,275,959 Patented Sept. 27, 1966 In the drawing:

FIG. 1 is a side view of a preferred circuit breaker structure incorporating the invention;

FIG. 2 is a top view of the breaker of FIG. 1;

FIG. 3 is an enlarged sectional view taken along the line 33 of FIG. 2 showing the breaker with the cover removed;

FIG. 4 is an enlarged isometric view of the thermal trip member and mounting bracket;

FIG. 5 is a corresponding view of the adjusting lever for the bracket;

FIG. 6 is an enlarged partial sectional view taken along the line 6-6 of FIG. 3 showing the breaker in the normal condition; and

FIG. 7 is a view corresponding to that of FIG. 6 showing the breaker with the adjusting lever inserted.

The breaker mechanism is mounted in a housing comprising a case 10 and cover 11 which preferably are permanently joined by rivets 12. A fixed contact 13 is mounted on a line terminal 14 within the housing (FIG. 3) with the line terminal exposed at a notch 15. A load terminal 16 is also positioned in the housing for receiving a conductor through an access opening 17, with a screw 18 providing for clamping the conductor in place. A moving contact 19 is carried on an arm 20, with the arm being moved between the contact closed position of FIG. 3 and a contact open position by a manually operated lever 21 and overcenter spring 22. The spring 22 is mounted at one end on the arm 20 and at the other end on a release lever 23. With the lever 23 in the position shown in FIG. 3, the breaker is operable as an on-off toggle switch.

The release lever 23 is maintained in the position of FIG. 3 by a trip member 30 pivotally mounted on a boss 31 with the end of the lever 23 resting on a bracket 32 of the trip member. When the trip member is moved counterclockwise removing the bracket 32 from engagement with the lever 23, the lever 23 moves clockwise and the arm 20 is moved counterclockwise, opening the switch. In the embodiment illustrated herein, the trip member 30 can be moved by a thermal responsive member 35 and by a magnetic armature 36.

The thermal responsive member 35, typically a bimetal strip, is mounted on a bracket 37 which in turn is mounted on the terminal 16 by a screw 38. The end of the bracket 37 carrying the terminal 16 fits in a space formed in the case 10 while the other end of the bracket to which the thermal responsive member is joined is free to move. The bimetal 35 and bracket 37 may be joined in a parallel plate structure by welding, as best seen in FIG. 4. The free end 35a of the thermal responsive member 35 is positioned adjacent a bracket 39 of the trip member 30 so that counterclockwise bending of the thermal responsive member will cause engagement with and corresponding counterclockwise movement of the trip member 30.

The armature 36 rests in a notch formed in a U-shaped magnetic structure 40. A core 41 is threadedly mounted in one end of the structure 40 and a coil 42 is wound on a coil form disposed over the core 41 with the coil form adhered to the magnetic structure 40. A spring 43 is positioned between the coil form and the armature 36 for urging the armature away from the core 41. The mag netic armature 36 is positioned to engage the end of the trip member 30 when the armature is moved clockwise so as to move the trip member counterclockwise.

The electrical circuit through the breaker runs from the line terminal 14 through the fixed contact 13 and moving contact 19 to the arm 20. A flexible conductor 50 provides connection from the arm 20 to one end of the coil 42 with the other end of the coil being fixed to the thermal responsive member 35. The circuit is completed from the thermal responsive member through the bracket 37 to the load terminal 16.

When the current through the breaker exceeds a predetermined value, the armature 36 will be attracted to the core 41- causing motion of the trip member 30 to release the lever 23 and open the switch. When an excess current exists in the breaker for a period of time sufiicient to produce heating and bending of the thermal responsive member 35 a particular amount, the trip member 30 will be engaged and moved counterclockwise, releasing the lever 23 and opening the switch. The heating and movement of the thermal responsive member may be achieved by various combinations of current magnitude and time and the breaker is normally calibrated by requiring tripping for a specified current and time.

The end of the core 41 remote from the armature 36 is slotted and is exposed to the exterior of the housing via a circular passage 50. After the breaker has been completely assembled, the current at which it will magnetically trip is set by turning the core 41 to vary the gap between the core and the armature. The amount of deflection required by the member 35 for tripping is also adjusted after final assembly by bending of the bracket 37 which carries the thermal responsive member 35. A portion of the bracket 37, preferably the end to which the thermal responsive member is joined, is positioned Within the housing adjacent an edge, as shown in FIG. 3. An adjustment tool, preferably in the form of a lever 51 with a knife-like end 52 may be inserted into the housing between the case and cover springing the members apart from the position of FIG. 6 to the position of FIG. 7. A notch 53 is provided at the end of the lever for engaging the bracket 37 permitting bending of the bracket and adjustment of the position of the thermal responsive member 35 relative to the trip member 30. When the breaker trips at the proper setting, the lever is removed and the breaker is ready for installation. While a slot may be provided in the housing for entry of the lever 51, a slot is not required and preferably is not utilized. Beveled edges 60, 61 may be provided on the cover and case to guide the entry of the lever for spreading of the housing members.

The breaker structure described herein provides for complete adjustment of the magnetic tripping mechanism and of the thermal tripping mechanism after the breaker has been finally and permanently assembled. This structure eliminates the problems inherent in adjustment prior to assembly and in maintaining adjustment during assembly. It should be noted that while the breaker illustrated utilizes both magnetic tripping and thermal tripping, breakers can be and often are provided only with thermal tripping and only with magnetic tripping.

Although an exemplary embodiment of the invention has been disclosed and discussed, it will be understood that other applications of the invention are possible and that the embodiment disclosed may be subjected to various changes, modifications and substitutions without necessarily departing from the spirit of the invention.

I claim as my invention:

1. In a circuit breaker having a releasable switch, the combination of:

a housing comprising first and second body members joined together along an edge;

a trip member mounted within said housing for releasing said switch;

a mounting bracket carried adjacent one end in said housing and having a plate-like section at the other end;

a thermal responsive member mounted on said platelike section, with a portion spaced from said bracket disposed for engaging said trip member;

an adjusting strip removably inserted between said body members along said edge for springing said body members apart and having a notch engageable with said bracket for bending said bracket and varying the position of said bracket and said thermal responsive member relative to said trip member; a magnetic structure carried within said housing; and a movable armature mounted on said structure and disposed for engaging said trip member;

said magnetic structure including a core threadedly mounted for movement toward and away from said armature, said housing including means defining an access opening to said core.

2. In a circuit breaker having a releasable switch, the

combination of:

a housing comprising first and second body members joined together along an edge;

a trip member mounted within said housing for releasing said switch;

a mounting bracket carried adjacent one end in said housing;

a thermal responsive member mounted on said bracket adjacent the other end thereof, with a portion spaced from said bracket disposed for engaging said trip member, and with said other end of said bracket disposed adjacent an edge of said housing;

with said bracket bendable for varying the position of said other end and said thermal responsive member relative to said trip member, and with said body members being spreadable providing access to said bracket;

an adjusting strip removably inserted between said body members along said edge for springing said body members apart, said strip being engageable with said bracket for bending said bracket and varying the position of said bracket and said thermal responsive member relative to said trip member;

a magnetic structure carried within said housing; and movable armature mounted on said structure and disposed for engaging said trip member;

said magnetic structure including a core threadedly mounted for movement toward and away from said armature, said housing including means defining an access opening to said core.

3. In a circuit breaker having a releasable switch, the

combination of:

a housing comprising first and second body members joined together along an edge;

a trip member mounted within said housing for releasing said switch;

a mounting bracket carried adjacent one end in said holiising and having a plate-like section at the other en a thermal responsive member mounted on said platelike section, with a portion spaced from said bracket disposed for engaging said trip member; and

an adjusting strip removably inserted between said body members along said edge for springing said body members apart and having a notch engageable with said bracket for bending said bracket and varying the position of said bracket and said thermal responsive member relative to said trip member.

4. In a circuit breaker having a releasable switch, the

60 combination of:

a housing comprising first and second body members joined together along an edge;

a trip member mounted within said housing for releasing said switch;

a mounting bracket carried adjacent one end in said housing;

a thermal responsive member mounted on said bracket adjacent the other end thereof, with a portion spaced from said bracket disposed for engaging said trip member, and with said other end of said bracket disposed adjacent an edge of said housing;

with said bracket bendable for varying the position of said other end and said thermal responsive member relative to said trip member, and with'said body members being spreadable providing access to said bracket; and

an adjusting strip removably inserted between said body members along said edge for springing said body members apart, said strip being engageable with said bracket for bending said bracket and 'varying the position of said bracket and said thermal responsive member relative to said trip member.

5. In a circuit breaker having a releasable switch, the

combination of:

a housing comprising first and second body members springably joined together along an edge to provide a normally closed access opening;

a trip member mounted Within said housing for releasing said switch;

a bendable mounting bracket carried in said housing;

a thermal responsive member mounted on said bracket,

References Cited by the Examiner UNITED STATES PATENTS 3/1952 Walker 200-88 7/1958 Cole ZOO-88 BERNARD A. GILHEANY, Primary Examiner.

R. N. ENVALL, JR., Assistant Examiner. 

3. IN A CIRCUIT BREAKER HAVING A RELEASABLE SWITCH, THE COMBINATION OF: A HOUSING COMPRISING FIRST AND SECOND BODY MEMBERS JOINED TOGETHER ALONG AN EDGE; A TRIP MEMBER MOUNTED WITHIN SAID HOUSING FOR RELEASING SAID SWITCH; A MOUNTING BRACKET CARRIED ADJACENT ONE END IN SAID HOUSING AND HAVING A PLATE-LIKE SECTION AT THE OTHER END; A THERMAL RESPONSIVE MEMBER MOUNTED ON SAID PLATELIKE SECTION, WITH A PORTION SPACED FROM SAID BRACKET DISPOSED FOR ENGAGING SAID TRIP MEMBER; AND 